Under almost all versions of gridiron football, offensive linemen cannot receive or touch forward passes, nor can they advance downfield in passing situations. To identify which receivers are eligible and which are not, football rules stipulate that ineligible receivers must wear a number between 50 and 79. This, however, can be circumvented in most leagues, most commonly by informing the referee of any player with a number in the ineligible range who lines up as an eligible receiver.